实现LoaderCallbacks接口动态循环加载网上图片并展示在手机屏幕上

1.布局xml文件

activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    tools:context=".MainActivity" >

    <Button

        android:id="@+id/btn"

        android:onClick="download"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:text="点击循环加载网上图片" />

    <ImageView 

        android:id="@+id/iv"

        android:layout_below="@id/btn"

        android:layout_height="match_parent"

        android:layout_width="match_parent"

        />

</RelativeLayout>

2.优化工具类ImageCach.java

package com.example.day15_ex_loadimage;

import java.util.HashMap;

import android.graphics.Bitmap;

/**

 * 图片下载存储优化工具类

 * @author Administrator

 *

 */

public class ImageCach {

    //存储url 和  图片解析流 Bitmap对象

public static HashMap<String,Bitmap>map=new HashMap<String, Bitmap>();

    //获取Bitmap对象

public static Bitmap getBitmap(String urlPath){

     return ImageCach.map.get(urlPath);

    }

//存放url Bitmap

public void put(String urlPath,Bitmap bm){

ImageCach.map.put(urlPath, bm);

}

}

3.联网获取图片类 HttpUtils.java

package com.example.day15_ex_loadimage;

import java.io.InputStream;

import java.net.HttpURLConnection;

import java.net.MalformedURLException;

import java.net.URL;

import android.graphics.Bitmap;

import android.graphics.BitmapFactory;

import android.util.Log;

public class HttpUtils {

    public static Bitmap getBitmap(String urlPath){

     Bitmap bm=null;

     bm=ImageCach.getBitmap(urlPath);//优化  防止重复下载

     if(bm==null){

     try {

URL url=new URL(urlPath);

HttpURLConnection conn=(HttpURLConnection) url.openConnection();

InputStream in=conn.getInputStream();

bm=BitmapFactory.decodeStream(in);

    ImageCach.map.put(urlPath, bm);

    Log.e("img","img");

    in.close();

    conn.disconnect();

     } catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

     }

     return bm;

    }

}

4.实现类 MainActivity.java

package com.example.day15_ex_loadimage;

import android.os.Bundle;

import android.annotation.SuppressLint;

import android.app.Activity;

import android.app.LoaderManager;

import android.app.LoaderManager.LoaderCallbacks;

import android.content.AsyncTaskLoader;

import android.content.Context;

import android.content.Loader;

import android.graphics.Bitmap;

import android.view.Menu;

import android.view.View;

import android.widget.ImageView;

@SuppressLint("NewApi")

public class MainActivity extends Activity implements LoaderCallbacks<Bitmap>{

    static int i=0;//控制图片url路径

    ImageView iv;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

        //初始化控件

iv=(ImageView) findViewById(R.id.iv);

}

public void download(View view){

LoaderManager loader=getLoaderManager();

loader.restartLoader(0,null,this);

}

@Override

public Loader<Bitmap> onCreateLoader(int id, Bundle args) {

MyLoader loader=new MyLoader(this);//创建loader对象

return loader;

}

@Override

public void onLoadFinished(Loader<Bitmap> arg0, Bitmap arg1) {

        iv.setImageBitmap(arg1);//设置图片在ImageView中显示

}

@Override

public void onLoaderReset(Loader<Bitmap> arg0) {

// TODO Auto-generated method stub

}

    private static class MyLoader extends AsyncTaskLoader<Bitmap>{

public MyLoader(Context context) {

super(context);

// TODO Auto-generated constructor stub

}

@Override

public Bitmap loadInBackground() {

    //只能加载4张图片 1-4.jpg

Bitmap bm=HttpUtils.getBitmap("http://www.ytmfdw.com/image/img"+(++i%4+1)+".jpg");

return bm;

}

@Override

protected void onStartLoading() {

// TODO Auto-generated method stub

super.onStartLoading();

    forceLoad();

}

    }

}

原文链接：http://www.apkbus.com/blog-813041-61198.html